Method for continuing measurements after recovery of a measuring tool immobilized in a well

ABSTRACT

A method for continuing a measuring operation using a sonde immobilized in the well which method involves lowering, concentric to the cable, a length of tubular elements until the sonde is engaged by a special coupling fitted at the end of the length of tubular elements, the length of tubular elements serving to protect the cable. In addition, a coupling at an upper end of the length of tubular elements is equipped with a lateral window to minimize maneuvering time. After engagement, the sonde is used to carry out measurements by displacing the length of tubular elements.

FIELD OF THE INVENTION

The present invention relates to a method for continuing measurementswhich have been interrupted or which have not started yet, when themeasuring sonde is immobilized in a well into which it has been loweredat the end of a maneuvering and measure transmission cable.

BACKGROUND OF THE INVENTION

There are several well-known methods for trying to grapple a measuringsonde whose handling is no longer possible through the cable, but noneallows measurements to be continued at the place where they have beenstopped following the immobilization of the sonde or its sticking.

A first method is common to all operations for fishing tubular partsstuck or lost in a wellbore. The well is first cleared of the measuringcable so that it does not hinder later operations. To that effect, thecable is pulled until it breaks at the brittle point which is located onthe fixing device on the upper part of the sonde. After taking up thecable by means of its winch, a fishing string mainly consisting of an"overshot", as it is commonly called in the profession, adapted toclutch the top of the sonde, is run down into the well. The othercomponents are conventionally pipes and drill collars. In this method,the difficulty consists of covering the sonde with the overshot in theabsence of guiding and while groping along from the surface. Thisoperation may actually only succeed at a slight depth and in instanceswhere the drill hole is well calibrated and where the axis of thetubular to be fished is almost parallel to the axis of the well.Concerning measuring sondes, most of them have a small diameter withrespect to the hole and these conditions are scarcely present, except insmall-diameter boreholes.

The most common method is called the "cut and thread" method. Itconsists of cutting the cable at the level of the derrick floor withoutdropping the part of the cable linked with the sonde into the well.Thus, the two ends of the cut cable are provided with two half-elementsconstituting a quick coupling. Assemblage of the overshot and of thefirst drill collars is started in the derrick. The end of the cableconnected to the winch is passed through these first elements when theyhang on the pipe hook. The two ends of the cable are connected throughthe quick coupling. The cable may then be maintained taut by its winchwhile the overshot and the first pipes are lowered around the latterinto the well. After hanging them onto the rotary table, the cable ismaintained before the quick coupling is opened so as to pass the end ofthe cable connected to the winch through new tubular elements assembledand hung on the pipe hook, as previously. The lowering maneuver iscontinued by repeating this operation until the overshot, guided by thecoaxial cable, covers and clutches the top of the sonde. The fishingoperation is ended, as in the previous method, after the cable has beenbroken.

This operation is long because passing the cable through each assembledlength of tubular elements causes a waste of time which is relativelyconsiderable in relation to the usual maneuver time. In case of stickingin a borehole, it is an accepted fact that speed is a preponderantfactor for the success of the fishing operation.

None of the two methods described above allows measurements to beachieved or continued with the sonde in said well.

The method in accordance with the present invention reduces the maneuvertime by limiting the number of operations for running the cable throughthe length of tubular elements, by using advantageously a side-entrysub.

With the "cut and thread method", the sonde is never connectedelectrically to the surface and it has never been attempted to keep theuse of the sensors of the sonde once the latter is stuck. In fact, theuse of a quick coupling including sealed connections for the conductorsis of no interest here since the cable will be broken after the sondehas been clutched. Furthermore, the cable being coaxial to the string oftubular elements over its total length, it is not possible to move thesonde while keeping the entire cable continuity.

The method of the invention also has the advantage of allowingmeasurements to be continued when the sonde has been clutched, be ittowards the bottom of the well or higher up towards the surface. Themeasuring operation, which has been interrupted or made impossible bythe immobilization of the sonde, will not be totally missed since it isnow possible, with the present method, to carry out the total or atleast part of the measuring program.

Besides the main advantage cited above, the invention provides a meansfor knowing precisely the moment of contact of the grappling sub withthe head of the sonde, then for checking the holding back of the sondeby said sub. In fact, the sonde is completely operational since it isconnected mechanically and electrically to the surface installation, asat the beginning of the operation. By means of sensors and through thetransmission of the signals towards the surface, the operator maycontrol that the displacement of the string makes the sonde moveidentically. This advantage guarantees not only that furthermeasurements will be possible, but also that grappling of the sonde willsucceed, unlike prior methods which provide no reliable information onthe quality of the grappling of the sonde, which accounts for therelatively high failure rate in the most difficult cases.

Another method called "side door" method may also illustrate the priorart. It consists of using a special overshot having a lateral openingallowing the measuring cable to be passed outside the fishing string.The cable needs not be cut. The string may then be lowered in aconventional way. The overshot is guided onto the head of the sonde asin the "cut and thread" method, then the operation is continuedaccording to the same methodology. This "side door" method is not usedfor wells deeper than 1,000 meters because it involves high risks ofdamage of the cable upon lowering of the string towards the well bottom,and in case of cable breakage, the absence of guiding of the overshotmost often compromises recovery of the sonde. In fact, when the overshotgets close to the head of the immobilized or stuck sonde, the well will,by that fact, give rise to considerable friction on the end of thestring outside which the cable is located and is therefore veryvulnerable. Moreover, the mechanical actions necessary to grapple thesonde are most often exceed the strength of conventional cables. Inorder to make the limited use of this method quite clear, the followingrecommendation, given to sonde fishing operators, may be cited: "theside door method should not be used to fish tools in open holes, butrather to fish tools stuck at the shoe of a casing string". But whenmeasuring tools are at this level, measurements are generally finished.

SUMMARY OF THE INVENTION

The method of the present invention allows operations in deep,difficult, deflected wells, and also in open holes, because the cable isonly present in the annulus defined by the tubular elements and the wellat a depth chosen by the operator, where he knows that the cable doesnot risk any damage. The cable is thus protected against outer frictionover a determined length with the method. The protection corresponds tothe length of the string between the grappling sub and the side-entrysub.

According to its claims, the present invention thus provides a methodallowing measurements to be continued by means of a measuring sondeimmobilized in a well, said sonde being connected to the surface by acable comprising at least one conductor connecting electrically saidsonde to a surface control installation, and said cable may be operatedby means of a winch.

The invention comprises the following stages :

cutting the cable substantially above the level of the rotary table,

fixing a half-connector on each of the two ends of the cut cable, saidhalf-connectors being adapted to constitute a quick coupling forassembling the two ends of said cable,

lowering into the well a tubular string for grappling the immobilizedsonde, said string comprising, in its inner channel, a the lower lengthof the cable substantially taut between said sonde and the derrickfloor, said string comprising at least one grappling sub adapted tograpple said sonde and a determined, length of maneuvering tubularselements,

fixing a side-entry sub onto the upper end of said determined length oftubular elements, said sub being adapted to pass said lower cable lengthfrom the inside to the outside of the tubular elements, connectingoutside the string the two ends of the cable and connecting saidconductors of said cable,

adding, above said sub, the corresponding length of tubular elements toreach the sonde immobilized in the well, while keeping said cablesubstantially taut,

guiding the string by means of the coaxial cable so as to grapple thesonde by way of said grappling sub,

carrying out measurements or servicings with said sonde grappled throughsaid grappling sub to the lower part of said string and linked to thesurface by said cable.

The method of the invention allows makes it possible to select thedetermined length of tubular elements contained between the grapplingsub and said side-entry sub substantially equal to a length ofmechanical protection of said cable, adapted both to reach the sondewith said grappling sub and to perform displacements during thecontinuation of the measurements without damaging the cable.

With the previous method, measurements may be carried out with saidgrappled sonde while going deeper than the depth of immobilization ofsaid sonde, by adding tubulars elements to the upper part of the string.Measurements may also be achieved with said grappled sonde while goinghigher than the depth of immobilization, by disassembling at most thelength of tubulars located above said side-entry sub, while keeping saidcable substantially taut.

The method may allow circulation of the drilling fluid by pumpingthrough the grappling string, the side-entry sub comprising seal meansaround the passage of the cable between the inside and the outside ofsaid string.

The invention may provide a method for detecting the grappling of thesonde through said overshot by means of the surface control installationconnected to the sonde by said conductors of said cable.

A mechanical quick coupling comprising means for connecting saidelectric conductors of said cable may also be used.

The method in accordance with the invention may allow the cable to bebroken at the brittle point located at the top of the sonde and to betaken up by means of the winch. The sonde is taken up to the surface bythe operation of pull-out of the string.

The previous method and all its variants may be used in oil wellbores,deflected or not with respect to the vertical, in which a measuring or aservicing sonde connected to the surface by a cable comprising at leastone electric conductor is immobilized. Said sonde cannot reach the zonesof said oil well in which measurements or servicings are performed byaction on the cable.

One particular application may be characterized in that the sonde isimmobilized by sticking in the well.

Another advantageous application may be characterized in that the sondecannot reach measurement or servicing zones because of the too highinclination of the well with respect to the vertical, which does notallow descent of said sonde by gravity.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will be clearfrom reading the description hereafter given by way of non limitativeexamples, with reference to the accompanying drawings, in which :

FIGS. 1A, 1B, 1C, 1D and 1E illustrate various stages of the grapplingof the sonde with the method of the invention;

FIGS. 2A and 2B show the measurement operations according to the methodof the present invention; and

FIG. 3 shows an embodiment of a side-entry sub.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1A shows a well comprising a cased length 2 and an open hole length3. A measuring or servicing sonde is immobilized in the open-holesection at a depth 25. The sonde has been lowered into the well by meansof cable 4 operated through winch 5 located at the surface. The cablecomprises conductors which connect electrically the sonde 1 to a controlinstallation 6.

In the following description of the present invention, the term depthwill refer to the length of the well measured from a fixed referencepoint located at the surface. It is generally the rotary table, but itmay also notably be measured from the ground or from the seafloor. Thechange of the measurement reference point will have no effect on thedescription and the scope of the invention.

Also, without departing from the scope of this invention, the sonde maybe immobilized at a depth where the well is cased, and similarly, thewell may have no cased length yet.

In the invention, the sonde operated through cable 4 may be stuckmechanically in the well in such a way that it cannot be taken up to thesurface or down towards the well bottom. Without departing from thescope of the invention, the sonde may be prevented from being displacedin only one direction, be it towards the surface or towards the bottom.This may be due to a partial mechanical sticking or to the fact that thewell inclination is such that the action of gravity is no longersufficient to allow descent of the sonde hanging on the end of cable 4.In this case, the sonde is immobilized when friction on the sondebecomes stronger than the force of gravity acting on the sonde. Theimmobilization depth may then be either the depth from which the sondecan no longer go down towards the well bottom, or a lower depth locatedabove the latter, because the operator preferably chooses, in this case,to set the method of the invention into action with a sonde which is notlaid on the walls of the well, but which hangs on the cable. To thateffect, he pulls on the cable so as to take the sonde up to a determineddepth.

In all the cases cited previously, the section of cable 4 connected tosonde 1 is supported by a conventional jaw device 9 set at the level ofa rotary table 8 of the derrick floor. The cable is cut substantiallyabove table 8 and two half-connectors 7 are fastened onto each end. Thequick coupling constituted by the two half-connectors is of aconventional type comparable to those used for the "cut and thread"method. Without departing from the scope of this invention, a specificquick coupling comprising means for connecting cable conductors may beused. This specific coupling may be, for example, a quick plug-in socketcapable of supporting the weight of the cable while connectingelectrically the sonde to installation 6, or more simply a quickmechanical coupling which also allows the conductors to be connected toone another. But, advantageously, the electric connections are onlyachieved when indispensable, that is when the side-entry sub is set onthe string.

After the stage illustrated by FIG. 1A, the operators assemble the firsttubular elements of the grappling string above the rotary table. Whenthe latter are still hanging on the lifting hook, the cable end 10connected to the winch is then passed through these first elements, thenthe two ends of the cable are linked by connecting the twohalf-connectors 7. Quick coupling 14 is constituted thereby.

FIG. 1B shows the stage where the first string elements 12 hang onelevators 30 and comprise at their end the grappling sub 11 adapted toco-operate with the head of the immobilized measuring sonde. Quickcoupling 14 being assembled, cable 4 is tightened through an action onwinch 5. The means 9 for hanging the cable are removed. The drillerlowers elements 12 into the well while keeping cable 4, located insideelements 12, substantially taut. The driller hangs them on the rotarytable with the conventional means used in the profession. It should benoted that cable 4 and consequently quick coupling 14 are stationarywith respect to the rotary table and that elements 12 are loweredconcentrically to said cable.

In FIG. 1C, the hanging means 9 are placed on the cable and the quickcoupling may then be disconnected.

The operators repeat the previous operations by passing the end of part10 of the cable through another length 13 of tubular elements. Afterconnection of the cable, the latter is tightened again, hanger 9 isremoved and element 13 is screwed onto element 12. The assembly islowered into the well and hung onto the table thereafter. Theseoperations follow one another until the desired string length includingthe cable in its inner channel is constituted. This length 16 is shownin FIG. 1D.

A side-entry sub 28 is screwed onto the upper end of the determinedlength 16. This device is adapted notably for three main functions:

passing a cable from the inner channel of a tubular element towards theoutside thereof,

forming a seal around the cable at the level of the window allowing theprevious function,

letting the cable free to slide in the window, at least in the directionof sliding from the inside towards the outside, that is when the cableis pulled by means of the winch.

Such a side-entry sub is well-known and may be illustrated notably bydocuments FR-2,502,236 or U.S. Pat. No. 4,607,693.

The end of the part of cable 4 connected to the sonde is passed throughthe opening of the side-entry of said sub and connected mechanically andelectrically to part 10 by means of a connector 27. This couplingrestores the electric continuity of the conductors of the cable, it hasto be drilling mud-tight and withstand a traction at least higher thanthe tensile strength of the cable. Without departing from the scope ofthis invention, a quick coupling 14 respecting the conditions stated forspecial coupling 27 may be used.

One operational difficulty then consists of screwing the side-entry subwhen the cable is passed through the opening of the window. In fact, itis recommended to avoid applying torsions and frictions onto the cable.This is why it may be advantageous to use a side-entry sub device suchas that illustrated in FIG. 3.

FIG.3 shows a sub referred to as a "three-part" sub. Element 31 is theside-entry sub proper, comprising a side entry 34 provided with asealing system and with a device for possibly fastening the cable. Thissub is screwed through a thread 39 onto another sub 32 comprising ascrewing ring 35. This ring rotates freely around the cylindricalextension 42 of sub 32. A device 37 holds ring 35 in a fixedlongitudinal position with respect to sub 32. This device may beconstituted from a circular ring in two parts screwed radially in agroove 43 machined in extension 42. This device will be dimensioned soas to support the weight hanging on the ring by means of thread 38. Asealing system 41 completes the assemblage of the ring on the extension.

The lower third sub 33 co-operates with a lower string of tubularelements through its thread 40. An antirotation system 36 fastens sub 33angularly with respect to sub 32.

Mounting of this three-part sub is achieved as follows:

screwing the lower sub 33 on the top of the tubular string of tubularelements hanging on the rotary table. The cable is kept coaxial,

elements 31 and 32 are previously screwed and locked by thread 39,

the cable being held on sub 33 by hanger 9, the free end is passedthrough opening 34 and connector 27 is assembled. The weight of thecable may then be controlled through winch 5, hanger 9 is removed,

placing assembly 31 and 32 onto sub 33 while making keying 36 coincide,

rotating ring 35 so as to screw the assembly 31 and 32 onto sub 33,without rotating the assembly with respect to sub 33. It should be notedthat the antirotation system 36 must have a sufficient length andlongitudinal play so as to be able to interlock at the beginning of thescrewing operation and to allow the displacement corresponding to thescrewing.

Determination of length 16 is important because it represents the wearbushing of the cable between the grappling sub and the side-entry sub.

In the example shown in FIG. D, the operators consider that the cable isin danger if it is in the annulus of the open hole, that is deeper thanthe shoe 26 of casing 2.

In order to reach the sonde immobilized at a distance 17 from the shoeand for the cable to be protected by the string in the total open-holesection, length 16 must be at least equal to the length 17 whichcorresponds to the length of the open-hole section between the shoe andthe immobilization depth.

If measurements are to be carried out deeper than the immobilizationpoint while keeping the cable protected in the total open-hole section,length 16 must be equal to the length of the open-hole section down tothe furthest measurement depth. If the well bottom is to be reached,length 16 must be equal to the total length of the open-hole section.

In the same instance, it is obvious that it will be possible to carryout measurements between immobilization depth 25 and shoe 26 whilekeeping the cable protected in the total open-hole section, except ifthe length of casing 2 is shorter than length 17.

Without departing from the scope of this invention, the cable protectionlength may be different from the length of the open-hole section betweenthe sonde and the shoe of the last casing. In fact, if part of the openhole, under the shoe, is properly calibrated and stable, it may bedecided to lower the side-entry sub 28 down to this zone and thus havethe cable in the uncased annulus.

It is actually advantageous to limit the length 16 of tubular elementspassing around the cable because it is a long and tedious operation. Butthe risks incurred will have to be assessed.

Conversely, if a casing exhibits sharp bends resulting from deflectionsprovided for example by a side tracking operation, it may then bedecided not to lower sub 28 deeper than the side track depth wheresticking of the cable through the tubulars can be foreseen. The sidetracking operation consists of plugging a well with cement at a certaindepth when the drilling operation can no longer be achieved as planned.A window is cut out in the casing, above the plug, and the well isdeflected by forming an S-shaped trajectory. This S-shaped trajectoryprovides considerable friction.

FIG. 1E shows the grappling 18 achieved by the grappling sub 11 on thehead of sonde 1. To reach this depth, the operators have assembled thelength 20 of tubular tubular elements in a conventional and thereforefaster way, without being hindered by a coaxial cable. Cable 4 exhibitsa length 19 in the casing-string annulus. During the descent of length20 of the grappling string, cable 4 is kept taut by means of winch 5.The sonde being still immobilized, the side-entry sub slides along thecable when the tubular string is lowered towards sonde 1.

When they get close to the head of the sonde, operators fasten acirculating head onto the upper part of the string so as to wash thegrappling sub through circulation in the string. As it has beenmentioned above, the side entry of sub 28 comprises a sealing system.

Gripping of the sonde is achieved through controlled tension on thecable and through the downward motion of the grappling sub. Operatorsfind their way about notably by measurement of the lengths and by thereactions of the sensors of the sonde since the latter remainsoperational by means of the connections established by connector 27.Grappling may be visualized by control installation 6.

If the sonde is stuck mechanically, it is released according to theusual procedure while having the possibility of controlling thedisplacement of the sonde.

FIG. 2A shows the descent of the sonde deeper below immobilization depth25 by a length shown here by bracket 21. The string length 22 representsin this case the sum of lengths 20 and 21. Measurements are carried outover this length 21 if need be. If the length 17 of the open-holesection between the immobilization point and shoe 26 is less than orequal to the depth of shoe 26, measurements may also be carried out overlength 17.

In all other cases, the maximum upper measurement depth is determinedwhen sub 28 is above ground.

If need be, it remains possible, at this stage of the method, to lowerthe measuring sonde into the well again so as to complete measurementsor to carry out other servicings.

When operations are to be ended, the side-entry sub 28 being aboveground, traction is applied onto cable 4 so as to break the brittlepoint 24 and the cable is entirely taken up through sub 28. When thisoperation is over, the sonde is taken up to the surface by disassemblingthe grappling string with the usual care.

Without departing from the scope of this invention, the well may be acomplete open hole comprising no casing.

This invention is not limited to servicings in an uncased or a partlycased well. It is actually applicable and very advantageous when themeasuring sonde run inside the casings is immobilized notably throughthe considerable friction provided by bends, deformations ordeteriorations in a zone of these casings.

I claim:
 1. A method for controlling measurements by means of a measuring sonde immobilized in a well, said sonde being connected to the surface by a cable comprising at least one conductor electrically connecting said sonde to a surface control installation, and said cable being operated by means of a winch, said method comprising the following stages:cutting the cable above the level of a rotary table of a derrick floor, fixing a half-connector onto each of the two ends of the cut cable, said half-connectors being adapted to constitute a quick coupling for assembling said cable, lowering into the well a tubular string for grappling the immobilized sonde, said string containing in its inner channel a lower length of the cable substantially taut between said sonde and the derrick floor, said string comprising at least one grappling sub adapted for grappling said sonde and a determined length of maneuvering tubular elements, fixing a side-entry sub onto the upper end of said determined length of tubular elements, said sub comprising a side wall passage through which said lower length of cable passes from the inside towards the outside of the tubular elements, connecting outside the string the two ends of the cable and connecting said conductors of said cable, adding above said sub a length of tubular elements adapted to reach the sonde immobilized in the well, while keeping said cable substantially taut, guiding the string by means of said lower length of cable so as to grapple the sonde by way of said grappling sub, carrying out measurements of servicings with said sonde fastened through said grappling sub to the lower part of said string and connected to the surface through said cable.
 2. A method as claimed in claim 1, further comprising:selecting the determined length of tubulars contained between the grappling sub and said side-entry sub substantially equal to a length of mechanical protection of said cable adapted both to reach the sonde with said grappling sub without damaging the cable and for displacements of the sonde during continuation of the measurements.
 3. A method as claimed in claim 1 or claim 2, comprising;carrying out measurements with said grappled sonde while going deeper than the point of immobilization of said sonde by adding tubular elements to an upper part of the string while keeping said cable substantially taut.
 4. A method as claimed in claim 1 or claim 2, comprising:carrying out measurements with said grappled sonde by going higher than the point of immobilization, by disassembling at most the length of tubular elements located above said side-entry sub while keeping said cable substantially taut.
 5. A method as claimed in claim 1, further comprising;circulating the drilling fluid by pumping through the grappling string, the side-entry sub comprising seal means around the passage of the cable between the inside and the outside of said string.
 6. A method as claimed in claim 1, further comprising:detecting the grappling of the sonde by said grappling sub by means of the surface control installation connected to the sonde by said conductors of said cable.
 7. A method as claimed in claim 1, further comprising:using a quick mechanical coupling to connect said cable, comprising means for connecting electric conductors of the cable.
 8. A method as claimed in claim 1, further comprising:breaking the cable at a the brittle point located at the top of the sonde, taking up the cable by means of the winch and taking the sonde up to the surface by the operation of pull-out of the string.
 9. Application of the method as claimed in claim 1 or claim 2 to an oil well deflected or not with respect to the vertical and in which a measuring or servicing sonde, connected to the surface by a cable comprising at least one electric conductor, is immobilized, and said sonde cannot reach the measuring or servicing zones of said oil well by action on the cable.
 10. Application as claimed in claim 9, wherein the sonde is stuck in said well.
 11. Application as claimed in claim 9, wherein the sonde cannot reach the measuring or servicing zones because of the too strong inclination of the well with respect to the vertical, which does not allow cable descent of said sonde by gravity. 